Copyright © 2011 Pearson Education, Inc. Approaches to Problem Solving

Copyright © 2011 Pearson Education, Inc. Slide 2-3 Unit 2B Standardized Units: More Problem-Solving Power

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-4 Standardized Unit Systems The International Metric System (or SI) Wide international use U.S. Customary System (USCS) (or English system) Used in the United States

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-5 Units of length were based on individual body measurements. A foot was once the length of the measurer’s foot. An inch was the thumb-width of the measurer. A mile was one thousand paces. There are three distinct sets of units used to measure weight. 1.Jewelers used troy measures of weight. 2.Pharmacists used apothecary measures of weight. 3.Other commerce was conducted with avoirdupois measures of weight. The basic unit of volume is the cubic inch (in. 3 ). Dry and liquid measures differ. U.S. Customary System

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-6 U.S. Customary System

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-7 U.S. Customary System

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-8 U.S. Customary System

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-9 International Metric System The metric system was designed to 1.replace many customary units with a few basic units. 2.simplify conversions through the use of a decimal (base 10) system. The following are basic metric units: meter (m) for length kilogram (kg) for mass second (s) for time liter (L) for volume

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-10 Metric Conversions Moving between metric units requires shifting the decimal place one to the right when going to the next smaller unit and one to the left when going to the next larger unit. (Example: 5.23 cm = 52.3 mm)

2-B Copyright © 2011 Pearson Education, Inc. Slide km = mi (1 km) 2 = ( mi) 2 Metric-USCS Conversions How many square miles are in a square kilometer? 1 km 2 ≈ mi 2

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-12 Temperature Units Three temperature scales are commonly used today. A temperature of 0 K is the coldest possible temperature, known as absolute zero.

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-13 Temperature Conversions The conversions are given in both words and with formulas in which C, F, and K are Celsius, Fahrenheit, and Kelvin temperatures, respectively. C = K  Subtract Kelvin to Celsius K = C Add Celsius to Kelvin Subtract 32. Then divide by 1.8 Fahrenheit to Celsius F = 1.8C + 32Multiply by 1.8. Then add 32. Celsius to Fahrenheit Conversion Formula Conversion in Words To Convert from

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-14 Units of Energy and Power Energy is what makes matter move or heat up. International metric unit is the joule Power is the rate at which energy is used. International metric unit is the watt A kilowatt-hour is a unit of energy. 1 kilowatt-hour = 3.6 million joules

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-15 Operating Cost of a Light Bulb A utility company charges 12.5¢ per kilowatt-hour of electricity. How much does it cost to keep a 75-watt light bulb on for a week? One watt = 1 joule/sec, so a 75-watt bulb uses 75 joules/sec. Find the number of joules used in a week:

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-16 Convert this result to kilowatt-hours: Now find the total cost: Operating Cost of a Light Bulb

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-17 Density describes compactness or crowding. Material density is given in units of mass per unit volume. e.g., grams per cubic centimeter (g/cm 3 ) Population density is given by the number of people per unit area. e.g., people per square mile (people/mi 2 ) Information density is given in units of mass per unit volume. e.g., gigabytes per square inch (GB/in. 2 ) Units of Density and Concentration

2-B Copyright © 2011 Pearson Education, Inc. Slide 2-18 The concentration of an air pollutant is often measured by the number of molecules of the pollutant per million molecules of air. e.g., parts per million (ppm) Blood alcohol content (BAC) describes the concentration of alcohol in a person’s body. e.g., grams of alcohol per 100 milliliters of blood Concentration describes the amount of one substance mixed with another. Units of Density and Concentration